The Quran itself boasts that no one can ever emulate its style or its miraculous content. Despite the fact that the Quran is a linguistic feat and a poetic miracle, by admission of Islamic scholars and sources, yet there is a structural flaw and a thematic fault in it. To be more specific, most Quran verses do not hold together thematically; there is no cohesion or coherence. Each Chapter of the Quran has a multitude of disconnected ideas and themes that do not relate to one another; sometimes the incongruity is inside the same verse. For example:

“And if you fear that you will not deal justly with orphans, then marry those that please you of women, two or three or four. But if you fear that you will not be just, then marry one only or those your right hand possesses. That is more convenient that you may not tend to injustice.” (Al-Nisaa, 3)

The above verse starts with talk about the possibility of doing injustice to orphans, then it suddenly shifts to licensing men to commit polygamy or to have concubines. The verse is completely incoherent like many parts of the Quran. The Arabic text sounds even more incoherent than the English translation, but some Muslim radicals try to justify the lack of coherence and the absence of cohesion by saying that the verse meant that marrying mothers of orphans will do justice for both (the mothers and the orphans). The verse does not say that meaning at all.
There are obvious reasons for these flaws: The Quran was “revealed” piecemeal, i.e., bit by bit over so many years. In addition, the collection of the Quran took place years after Muhammad’s death, and the death of the prophet’s companions who memorized it; also, the collection itself was a primitive and a shoddy process. Finally, there were many interpolations and changes that were done in the Quran as it will be shown later in Chapter 12 of my book, The Unknown History of Islam.

The Quran was written in classical Arabic in the first half of the Seventh Century CE, and used the dialect of Mecca, specifically the dialect of its biggest tribe in Mecca, the tribe of Quraish. This is one proof that it is not universal or eternal as Muslims claim but written by a native of Quraish, using a local dialect.